The more suprinate your wrists are, the stronger your biceps are. The biceps are weakest when using a pronated grip and strongest when using a supianted grip. The "neutral" grip is just somewhere in between. The issue when pulling is that the biceps generally fatigue faster than the lats, so the lats will get a better workout if the biceps last longer. When using a neutral grip, you'll work the lats better than while using a pronated grip, but not as good as while using a supinated grip.